drivers/char/hw_random/npcm-rng.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2019 Nuvoton Technology corporation.
   3
   4 #include <linux/kernel.h>
   5 #include <linux/module.h>
   6 #include <linux/io.h>
   7 #include <linux/iopoll.h>
   8 #include <linux/init.h>
   9 #include <linux/random.h>
  10 #include <linux/err.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/hw_random.h>
  13 #include <linux/delay.h>
  14 #include <linux/of_irq.h>
  15 #include <linux/pm_runtime.h>
  16 #include <linux/of_device.h>
  17
  18 #define NPCM_RNGCS_REG          0x00    /* Control and status register */
  19 #define NPCM_RNGD_REG           0x04    /* Data register */
  20 #define NPCM_RNGMODE_REG        0x08    /* Mode register */
  21
  22 #define NPCM_RNG_CLK_SET_62_5MHZ        BIT(2) /* 60-80 MHz */
  23 #define NPCM_RNG_CLK_SET_25MHZ  GENMASK(4, 3) /* 20-25 MHz */
  24 #define NPCM_RNG_DATA_VALID     BIT(1)
  25 #define NPCM_RNG_ENABLE         BIT(0)
  26 #define NPCM_RNG_M1ROSEL        BIT(1)
  27
  28 #define NPCM_RNG_TIMEOUT_USEC   20000
  29 #define NPCM_RNG_POLL_USEC      1000
  30
  31 #define to_npcm_rng(p)  container_of(p, struct npcm_rng, rng)
  32
  33 struct npcm_rng {
  34         void __iomem *base;
  35         struct hwrng rng;
  36         u32 clkp;
  37 };
  38
  39 static int npcm_rng_init(struct hwrng *rng)
  40 {
  41         struct npcm_rng *priv = to_npcm_rng(rng);
  42
  43         writel(priv->clkp | NPCM_RNG_ENABLE, priv->base + NPCM_RNGCS_REG);
  44
  45         return 0;
  46 }
  47
  48 static void npcm_rng_cleanup(struct hwrng *rng)
  49 {
  50         struct npcm_rng *priv = to_npcm_rng(rng);
  51
  52         writel(priv->clkp, priv->base + NPCM_RNGCS_REG);
  53 }
  54
  55 static int npcm_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  56 {
  57         struct npcm_rng *priv = to_npcm_rng(rng);
  58         int retval = 0;
  59         int ready;
  60
  61         pm_runtime_get_sync((struct device *)priv->rng.priv);
  62
  63         while (max) {
  64                 if (wait) {
  65                         if (readb_poll_timeout(priv->base + NPCM_RNGCS_REG,
  66                                                ready,
  67                                                ready & NPCM_RNG_DATA_VALID,
  68                                                NPCM_RNG_POLL_USEC,
  69                                                NPCM_RNG_TIMEOUT_USEC))
  70                                 break;
  71                 } else {
  72                         if ((readb(priv->base + NPCM_RNGCS_REG) &
  73                             NPCM_RNG_DATA_VALID) == 0)
  74                                 break;
  75                 }
  76
  77                 *(u8 *)buf = readb(priv->base + NPCM_RNGD_REG);
  78                 retval++;
  79                 buf++;
  80                 max--;
  81         }
  82
  83         pm_runtime_mark_last_busy((struct device *)priv->rng.priv);
  84         pm_runtime_put_sync_autosuspend((struct device *)priv->rng.priv);
  85
  86         return retval || !wait ? retval : -EIO;
  87 }
  88
  89 static int npcm_rng_probe(struct platform_device *pdev)
  90 {
  91         struct npcm_rng *priv;
  92         int ret;
  93
  94         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  95         if (!priv)
  96                 return -ENOMEM;
  97
  98         priv->base = devm_platform_ioremap_resource(pdev, 0);
  99         if (IS_ERR(priv->base))
 100                 return PTR_ERR(priv->base);
 101
 102         dev_set_drvdata(&pdev->dev, priv);
 103         pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
 104         pm_runtime_use_autosuspend(&pdev->dev);
 105         pm_runtime_enable(&pdev->dev);
 106
 107 #ifndef CONFIG_PM
 108         priv->rng.init = npcm_rng_init;
 109         priv->rng.cleanup = npcm_rng_cleanup;
 110 #endif
 111         priv->rng.name = pdev->name;
 112         priv->rng.read = npcm_rng_read;
 113         priv->rng.priv = (unsigned long)&pdev->dev;
 114         priv->clkp = (u32)(uintptr_t)of_device_get_match_data(&pdev->dev);
 115
 116         writel(NPCM_RNG_M1ROSEL, priv->base + NPCM_RNGMODE_REG);
 117
 118         ret = devm_hwrng_register(&pdev->dev, &priv->rng);
 119         if (ret) {
 120                 dev_err(&pdev->dev, "Failed to register rng device: %d\n",
 121                         ret);
 122                 pm_runtime_disable(&pdev->dev);
 123                 pm_runtime_set_suspended(&pdev->dev);
 124                 return ret;
 125         }
 126
 127         return 0;
 128 }
 129
 130 static int npcm_rng_remove(struct platform_device *pdev)
 131 {
 132         struct npcm_rng *priv = platform_get_drvdata(pdev);
 133
 134         devm_hwrng_unregister(&pdev->dev, &priv->rng);
 135         pm_runtime_disable(&pdev->dev);
 136         pm_runtime_set_suspended(&pdev->dev);
 137
 138         return 0;
 139 }
 140
 141 #ifdef CONFIG_PM
 142 static int npcm_rng_runtime_suspend(struct device *dev)
 143 {
 144         struct npcm_rng *priv = dev_get_drvdata(dev);
 145
 146         npcm_rng_cleanup(&priv->rng);
 147
 148         return 0;
 149 }
 150
 151 static int npcm_rng_runtime_resume(struct device *dev)
 152 {
 153         struct npcm_rng *priv = dev_get_drvdata(dev);
 154
 155         return npcm_rng_init(&priv->rng);
 156 }
 157 #endif
 158
 159 static const struct dev_pm_ops npcm_rng_pm_ops = {
 160         SET_RUNTIME_PM_OPS(npcm_rng_runtime_suspend,
 161                            npcm_rng_runtime_resume, NULL)
 162         SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 163                                 pm_runtime_force_resume)
 164 };
 165
 166 static const struct of_device_id rng_dt_id[] __maybe_unused = {
 167         { .compatible = "nuvoton,npcm750-rng",
 168                 .data = (void *)NPCM_RNG_CLK_SET_25MHZ },
 169         { .compatible = "nuvoton,npcm845-rng",
 170                 .data = (void *)NPCM_RNG_CLK_SET_62_5MHZ },
 171         {},
 172 };
 173 MODULE_DEVICE_TABLE(of, rng_dt_id);
 174
 175 static struct platform_driver npcm_rng_driver = {
 176         .driver = {
 177                 .name           = "npcm-rng",
 178                 .pm             = &npcm_rng_pm_ops,
 179                 .of_match_table = of_match_ptr(rng_dt_id),
 180         },
 181         .probe          = npcm_rng_probe,
 182         .remove         = npcm_rng_remove,
 183 };
 184
 185 module_platform_driver(npcm_rng_driver);
 186
 187 MODULE_DESCRIPTION("Nuvoton NPCM Random Number Generator Driver");
 188 MODULE_AUTHOR("Tomer Maimon <[email protected]>");
 189 MODULE_LICENSE("GPL v2");